Shaft furnace with evaporation cooling

ABSTRACT

This invention relates to an improved shaft furnace of the type which over at least part of its outer surface is provided with a double wall, the space enclosed by said double wall being part of a circulation system for cooling liquid without pressure, there being a reservoir above the double wall space, in which evaporated cooling liquid can be separated from the cooling mixture, which reservoir is in direct open communication with the upper end of the double wall space, said space being divided into two spaces by an intermediary baffle being about parallel to the outer surface of the furnace, said two spaces being in open communication with each other at their upper and lower ends as set forth in U.S. Pat. application Ser. No. 190,745, filed Oct. 20, 1971, now U.S. Pat. No. 3,750,629.

[1.11 3,820,509 June 28, 1974 1 SHAFT FURNACE WITH EVAPORATION COOLING [75] lnventor: Cornelis Van Der Vliet, Akersloot,

Netherlands [73] Assignee: Hoogovens ljmuiden B.V., ljmuiden,

Netherlands [22] Filed: Jan. 10, 1973 [21] Appl. No.: 322,471

[30] Foreign Application Priority Data 7 Netherlands 7200418 Jan. 11.1972

[52] US. Cl. 122/6 R, 266/32 [51] Int. C1.,. F221) 37/00 [58] Field of Search 122/6 R, 6 A, 266/32 [56] References Cited UNITED STATES PATENTS 452,607 5/1891 Hunt 122/6 1,126,028 1/1915 Kekich 2,824,731 2/1958 Schwengel 266/32 3,345,057 10/1967 Mitchell et al..... 266/32 X Primary ExaminerKenneth W. Sprague Attorney, Agent, or Firm-Hall & Houghton [5 7] ABSTRACT This invention relates to an improved shaft furnace of the type which over at least part of its outer surface is provided with a double wall, the space enclosed by said double wall being part of a circulation system for cooling liquid without pressure, there being a reservoir above the double wall space, in which evaporated cooling liquid can be separated from the cooling mixture, which reservoir is in direct open communication with the upper end of the double wall space, said space being divided into two spaces by an intermediary baffle being about parallel to the outer surface of thefurnace, said two spaces being in open communication with each other at their upper and lower ends as set forth in U.S.' Pat. application Ser. No. 190,745, filedtOct, 20, 1971, now US. Pat. No. 3,750,629.

8 Claims, 7 Drawing Figures PATENTEDJUHZB 1914 SHEET 1 [IF 2 SHAFT FURNACE WITH EVAPORATION a COOLING ing pig iron.

' This invention relates to an improved shaft furnace of the type which over at least part of its outer surface is provided with a double wall, the space enclosed by said double wall being part of a circulation system for cooling liquid without pressure, there being a reservoir above the double wall space, in which evaporated cooling liquid can be separated from the cooling mixture, which reservoir is in direct open communication with the upper end of the double wall space, said space being divided into two spaces by an intermediary baffle being about parallel to the outer surface of the furnace, said two spaces being in open communication with each other at their upper and lower ends, as given in patent application Ser. No. 'l90,745 now US. Pat. No. 3,750,629. 1

Due to the embodiment of the circulation system for cooling liquid as described in said prior application it has appeared possible to obtain an effective and reliable cooling' with simple and relatively inexpensive means according to the principle of evaporation cooling for parts of furnace walls. As a result thereof it ap pears that, in particular for large and, thermally very highly loaded furnaces, a more uniform cooling can be obtained, which also results in less wear of the refractory lining of the furnace.

When applying this type of cooling to a blast furnace this cooling system was up to now only applied in the zone of the so-called bosh of the furnace. It .is usual to apply spray cooling by liquid in the zone of the socalled hearth of the furnace.

In the zone of the bosh of the furnace the refractory masonry work is pushed outwardly onto the outer metal jacket due to the tapered shape of this bosh and gravity. This causes such an intimate contact that there are no particular problems for a good heat transfer from the interior of the furnace through the masonry structure and the metal jacket to the cooling system.

, However, in coolingthe shaft or stack of a blast fur nace, which tapers so as to become narrower upwardly, a problem is posed by the fact that the refractory lining requires special provisions to remain in good contact with the outer metal jacket. This is of course so because the masonry work of this part of the furnace will have the tendency to separate from the metal jacket surrounding it in view of this taper, which tendency is In view of all such and other considerations there has up to now been the opinion among experts that the cooling system given in application Ser. No. 190,745 now US. Pat. No. 3,750,629 should only extend along the bosh of the furnace, mainly in view of the fact that it was not deemed possible to maintain a good heat transmitting contact between the masonry of the furnace shaft or stack and the metal jacket surrounding it. Another consideration was that it was deemed impossible or quite unsuitable to have the cooling system extend along a rather sharp bend in the furnace wall as thiswould unfluence the evaporation cooling in a disadvantageous manner. However, it has appeared according to the present invention that it is possible to overcome such difficulties and objections, if and in so far as present.

In view thereof the present improvement consists in that a number of such circulation systems formed by a double-walled space are applied one above the other along several parts of the outer surface of the furnace, which systems operate essentially independently of one another. In this way his possible to apply mutually independent cooling systems along parts of a furnace wall, which each do not show any bends or substantially no bends along their height. It has appeared that it is quite well possible to maintain such a good heat transfer contact between the refractory masonry structure in the furnace shaft or stack and the metal jacket surrounding it that the invention can be made quite effective in this part of the furnace.

The most important advantages of the suggested improvement can be obtained if two circulation systems are applied, a lower one around part of the bosh of the furnace and an upper one around at least the lower part of the shaft or stack of the furnace. Moreover, advantages are obtainable by such circulation system around the furnace hearth and another such system around part of the bosh.

Although it is possible to have the upper circulation system of such a set extend over the entire height of the furnace shaft or stack, it appears preferable on the basis of considerations about process technology and design to cool the upper part of the shaft or stack in a more traditional way.

In this respect'it is possible to cool this upper part of the furnace shaft'or stack'in a usual manner with the aid of cooling plates extending into the refractory masonry of the furnace, and it is also possible according to the invention to cool this part of the furnace with the aid of panel cooling elements known as such (stavecoolers). In order to obtain a sufficient cooling also in the region of the transition zone between the two circulation systems, which, for the zone between bosh and shaft or stack, is the zone where usually the supporting annulus of the furnace is situated, which annulus supports the shaft or stack separately from the lower structure of thefurnace, it is possible to have the lower dou' ble wall structure extend upwardly into close proximity of said supporting annulus and to have the upper double wall cooling structure extend downwardly also into close proximity of said supporting annulus. Nevertheless it appears with such possibilities that the cooling of the transition zone may cause difficulties, which according to the invention can be avoided by embodying the transition zone between the two circulation systems as a cooling jacket, which is hollow in its interior between double walls and into and out of which water is adapted to flow, the discharge of which water from said jacket being preferably part of the supplementing system for supplementing evaporated cooling water in at least one of the two circulating systems.

It has already been remarked that it has appeared possible to apply provisions in the zone of the upper circulation system in order to keep the refractory masonry-work in contact with the metal jacket. According to a possible and preferred embodiment of such a structure such provisions according to the invention consist of anchors, which are secured to the metal jacket, extend inwardly and which anchor the refractory structure to this jacket. Another possible structure according to the invention consists in that the liquid cooled cooling plates extend through the double wall cooling space and into the masonry structure. The double walls should in this case in the zone of these cooling plates be provided with a hollow sleeve, which allows a complete separation of the cooling plate with respect to the space in the double wall. As in this case the cooling plates only have a supporting function for the masonry and hardly a cooling function, it is possible to apply only a very small number of said cooling plates. Nevertheless it has appeared that they may constitute a considerable complication of the design, and also that they may have a harmful effect on the operation of the evaporation cooling. In view thereof it is according to the invention preferred to apply a structure in which the refractory masonry work of the furnace wall itself is embodied in such a way that it will remain in contact with the surrounding metal jacket without special anchoring means or the like. This is e.g. obtainable by building the refractory masonry work of the wall of the furnace according to the invention at least in part with bricks of mutually interlocking shape. It is also possible according to the invention to embody the refractory masonry at least in part with refractory bricks of which the upper and lower surfaces, in assembled condition, are inclined downwardly in a radially outward direction with respect to the furnace. In that case all the downwardly directed forces exerted on these bricks, with the exception of the lower bricks, will have a component which urges these bricks radially outwardly.

The invention will now be explained in more detail with reference to the enclosed drawings by way of example only.-

FIG. 1 shows diagrammatically a blast furnace with a cooling system according to the invention in vertical section.

FIG. 2 shows part of a blast furnace wall on a larger scale than FIG. 1 in vertical section.

FIG. 2a is a detail from FIG.' 2 according to a somewhat different embodiment.

FIG. 3 is another detail of FIG. 2 on a considerably enlarged scale and in a different embodiment.

FIGS. 4, 5 and 6 are further and different details of the structure of FIG. 2.

FIG. 1 shows partly in longitudinal vertical section and partly in view a blast furnace l diagrammatically. Around the bosh 2 of the furnace a cooling system is provided according to patent application Ser. No. 190,745 now U.S. Pat. No. 3,750,629, and around shaft or stack 12 a second similar cooling system is provided. Both cooling systems have been shown only in part and diagrammatically in FIG. 1. In essence they consist of a double wall, which in peripheral direction is built up from a set of sections. Reference numerals 3, 4 and 7,

8 respectively show two of said sections. At the upper end of'the double walls steam discharge ducts are connected thereto andtwo of said ducts of each set of sec tions are indicated by reference numerals 5, 6 and 9, 10 respectively. A further description and explanation about the function and operation of the cooling systems has been given in the above-indicated prior patent application, to which it is referred here, so that no detailed description thereof will be necessary in this specification. In the zone of the transition between the bosh 2 to the shaft or stack 12 there is the usual metal structure including the supporting annulus 11 for the shaft or stack, which make a close contact between the two cooling systems impossible.

FIG. 2 shows the part of the furnace wall at the height of the cooling systems 4 and 8 in more detail. From this Figure it is clear that the supporting annulus l l is supported by columns 13, forming part of a metal structure, which, however, is not essential for the present invention and is usual and known to the experts. The cooling system 4 extends from a short distance above the blast nozzles (tuyeres) 14 up to full or close proximity to the supporting annulus 11. In this cooling system an annular intermediary baffle 17 and a deflecting and splash baffle 18 are positioned, which take care of a circulating flow within the cooling system 4 and a division in the water flow for water droplets entrained by the steam, as fully described in the above-mentioned prior patent application. In a similar manner baffles l9 and 20 are provided within cooling system 8 as shown. In this drawing a panel cooler (stave-cooler) 15 is shown above cooling system 8 in the wall of the shaft or stack 12 of the furnace. The embodiment and operation of such a cooler is generally known for the experts, so that it will not be necessary to describe it here in more detail.

In the zone of the shaft or stack 12 provisions such as steel anchors 25 are connected as by welding to the surrounding steel jacket, said anchors 25 extending into the masonry structure and serving to anchor this structure to the steel jacket. Such anchors may be hollow and water may be circulated through them for cooling them.

In FIG. 2a the upper end of FIG. 2 is shown on an enlarged scale and in a somewhat different embodiment. Instead of stave-coolers a number of cooling plates of usual design is applied, two of them being shown and indicated by 16 and 17.

In the structure of FIG. 2 supplementing water is supplied above the deflecting and splash baffles l8 and 20 by usual means not shown. The water supplementing the water in the system and present above the deflecting baffle 18 serves for cooling the transition zone between the cooling systems 4 and 8. If this cooling is not sufficient it is possible to use a different embodiment such as the embodiment shown in FIG. 3 on an enlarged scale. In this Figure the space between the deflecting baffle 18 and the supporting annulus 11 is embodied as an annular space all around the furnace and limited by bellows 22, through which water passes. The water after flowing through this entire annular space is thereupon guided over deflecting baffle 18 as supplementing water in the cooling system 4.

FIG. 4 shows a different embodiment for an anchoring part to anchor the refractory masonry of the shaft 12 of the furnace to the surrounding metal jacket, there being shown an anchor 25 formed by a cooling plate 26 of usual design, which extends through the cooling system 8 into the masonry structure of shaft 12. To obtain this design there is a sleeve where the cooling plate 26 extends through the double wall cooling system 8, said sleeve avoiding that the cooling water will leak outwardly from the double wall space 8 along the cooling plate 26 outwardly. The cooling plate 26 is secured to the cooling system 8 by a flange 27. Through supply and discharge ducts 28 and 29 cooling water circulates through the cooling plate 26.

In FIG. 5 part of the furnace wall in the area of the shaft or stack 12 has been shown in horizontal section. This Figure shows an embodiment of the furnace in which without provisions secured to the steel jacket an intimate contact between the refractory masonry and the jacket is warranted. To this end the bricks of the layer 23, which is closest to the interior of the furnace, and the bricks of the layer 24, which is in contact with the outer metal jacket, are each provided with dovetailed protrusions and corresponding recesses. If during the construction of the refractory masonry of the furnace the layer 24 is tightly mounted into contact with the furnace wall, such dove-tailed parts will avoid that the inner layer of bricks will separate and loose contact with the outer layer. I

FIG. 6 shows an alternative embodiment in longitudinal vertical section through part of the wall. In this embodiment the bricks of the layers 23 and 24 have upper and lower surfaces which are inclined downwardly in a radially outward direction. This results in a situation in which forces which are exerted on the inner layer 23 of the masonry structure by the own weight of the bricks and by the downward movement of the charge in the furnace will give a component of force which is directed radially outwardly. This component will entrain that the masonry structure in operation will remain in contact with the outer jacket or wall of metal under some pressure.

It will be clear that many other differences in embodiment are possible for the structure of the masonry work in the shaft or stack 12 while using the cooling system according to the invention. It will also be clear that the invention is not restricted to the application with a blast furnace, but that it may in a corresponding way be applied for other types of furnaces, in which the height of the wall to be cooled or the shape thereof with a bend or an upwardly narrowing taper will make a subdivision of the system of evaporation coolingdesirable.

I-claim:

. 1. In an improved vaporization cooled furnace of the type having a circulating system for cooling liquid in which said system includes a double walled portion extending over at least a part of the outer surface of the furnace and defining a circulating space for said liquid, a vapor separating reservoir positioned immediately on top of said double walled portion and having a direct open communication with the upper end of said circulating space, vapor venting means in communication with said vapor separating reservoir, baffle means positioned in the space below said vapor separating reservoir, and being about parallel to the outer surface of the furnace, said baffle means dividing the space into inner liquid and vapor upflow and outer liquid downflow spaces in open communication with each other at their upper and lower ends, and means for establishing a liquid level in said outer downflow space in proximity to the upper end of said baffle means and below said vapor separating reservoir, the improvement comprising positioning a plurality of the circulating systems one above the other along parts of the outer surface of the furnace, each of said systems being operated independent of one another.

' 2. A furnace in accordance with claim 1, wherein said circulating systems are two in number, one being provided around part of the furnace bosh and the other being provided around the lower part of the furnace shaft.

3. A furnace in accordance with claim 2, wherein the remaining part of the furnace shaft is provided with cooling plate means which extend from the outside thereof into the refractory masonry work ofthe furnace.

4. A furnace in accordance with claim 2, wherein the remaining part of the furnace shaft is provided with cooling panels.

5. A furnace in accordance with claim 2, wherein a transition zone is formed between the two circulating cooling systems, said transition zone being a cooling hollow jacket having an inlet and outlet through which water will flow to obtain the desired cooling effect.

6. A furnace in accordance with claim 5, wherein the outlet for the water from said cooling jacket is part of the supplementing system of at least one of the said two circulating cooling systems to make up for the cooling water evaporated therein.

7. A furnace in accordance with claim 2, wherein the zone of the upper circulating cooling system includes means for keeping the refractory masonry work in contact with the outer furnace wall.

8. A furnace in accordance with claim 7, wherein said means include cooling plates extending through the double wall space of the upper circulating cooling system and into the masonry structure, said cooling plates being provided with means permitting liquid flow for cooling said plates internally. 

1. In an improved vaporization cooled furnace of the type having a circulating system for cooling liquid in which said system includes a double walled portion extending over at least a part of the outer surface of the furnace and defining a circulating space for said liquid, a vapor separating reservoir positioned immediately on top of said double walled portion and having a direct open communication with the upper end of said circulating space, vapor venting means in communication with said vapor separating reservoir, baffle means positioned in the space below said vapor separating reservoir, and being about parallel to the outer surface of the furnace, said baffle means dividing the space into inner liquid and vapor upflow and outer liquid downflow spaces in open communication with each other at their upper and lower ends, and means for establishing a liquid level in said outer downflow space in proximity to the upper end of said baffle means and below said vapor separating reservoir, the improvement comprising positioning a plurality of the circulating systems one above the other along parts of the outer surface of the furnace, each of said systems being operated independent of one another.
 2. A furnace in accordance with claim 1, wherein said circulating systems are two in number, one being provided around part of the furnace bosh and the other being provided around the lower part of the furnace shaft.
 3. A furnace in accordance with claim 2, wherein the remaining part of the furnace shaft is provided with cooling plate means which extend from the outside thereof into the refractory masonry work of the furnace.
 4. A furnace in accordance with claim 2, wherein the remaining part of the furnace shaft is provided with cooling panels.
 5. A furnace in accordance with claim 2, wherein a transition zone is formed between the two circulating cooling systems, said transition zone being a cooling hollow jacket having an inlet and outlet through which water will flow to obtain the desired cooling effect.
 6. A furnace in accordance with claim 5, wherein the outlet for the water from said cooling jacket is part of the supplementing system of at least one of the said two circulating cooling systems to make up for the cooling water evaporated therein.
 7. A furnace in accordance with claim 2, wherein the zone of the upper circulating cooling system includes means foR keeping the refractory masonry work in contact with the outer furnace wall.
 8. A furnace in accordance with claim 7, wherein said means include cooling plates extending through the double wall space of the upper circulating cooling system and into the masonry structure, said cooling plates being provided with means permitting liquid flow for cooling said plates internally. 